Process for finishing leather articles



Patented Aug. 9, 1938 Hans Freudenberg and Philipp Haas, Weinheim, Germany, assignors to Freudenberg & 00. G. m. b. 11., Frankfort-on-the-Main, Germany a German company No Drawing. Application November 1, 1934, Se- 4 rial N0. 751,113. In Germany August 28, 1933 10 Claims. (Cl. 12-142) (Lit For the manufacture of leather goods, particularly high-grade footweanleather which has been dressed in the leather factory is in general employed. This process of dressing consists in rivatives, of rubber, may also be employed, if

desired in cooperation with the foregoing. In many cases it has proved to be advantageous to 5 several individual treatments, which commence apply to the leather articles several polymers 5 after the drying of the leather, such as pressing, of acrylic compounds as aforesaid in combinapommelling, polishing, pounding, ironing and the tion, for example in the form of mixed polymers 7 like, some of which are several times repeated. or mixtures of polymers, or in succession.

In the manufacture of shoes, boots and other The solutions or emulsions may also contain 10 articles from leather dressed in the leather facadmixtures for improving their properties, for 10 tory, the leather more or less loses its good apexample softeners such as tricresyl phosphate or pearance-it becomes dull andsoiled or stained. castor oil, oils suchas oil of turpentine, wetting. It is consequently necessary to impart a satisagents such as alcohol, protective colloids such factory appearance to the footwear by the apas rubber latex or tragacanth, gloss-imparting l5 plication of so-called finishes. The finishing of agents such as shellac and albumin, if desired 1:; leather goods has in general been hitherto ef-, several of such admixtures In many cases it fected by first washing them, whereby the dresshas proved to be advantageous also to add drying produced in the leather factory is to a coning oils. siderable extent again removed, and then ap- According to an important embodiment of this plying the usual shoe-finishing preparations, invention pigment colours or soluble dyestuffs or 20 which are, for example, prepared from shellac, colours of both kinds are incorporatedwith the wax and the like materials. solutions or emulsions. In this way it is possible This invention has as its object the manufacto impart any desired colour to the footwear, ture from non-dressed or only partially dressed for example shoes, during the finishing process.

5 leather of finished articles, particularly foot- The polymers of acrylic compounds may be as wear, which satisfy the present high requiredissolved in the usual organic solvents and be ments, particularly with regard to colour, purity employ d in the form of such solutions. which, of colour, gloss or polish and the like. may, if desired, also contain certain admixtures.

, According to this invention it has'been found In the case of chlorinated rubber solutions an that goods or articles manufactured from nonaddition of castor oil has in many cases proved an dressed or only partially dressed leather, parto be advantageous. ticularly footwear, i. e. goods or articles which, It has however been found according to this owing to their appearance, especially with regard invention that the use of expensive organic solto colour and polish, are not customarily marvents can be entirely or to a large extent avoided v keted, can be converted into high-grade goods, and that the polymers of acrylic compounds can 35 which satisfy all trade requirements, by employbe employed i e o m o aqueo emu si s. ing for the finishing of'the non-dressed or only which are free'fi'om Organic ve ts ay, i partially dressed leather articles, particularly desired, also contain re vely Small q iti of footwear, solutions or preferably aqueous emulorgfinic llqllids- Th se aq 1 1 y.

40 sionspf polymers of acrylic compounds, which, a p be P p d follows! 4( because of the size of the molecule or molecular Starting materials. which re capable of Y framework, remain adhering substantially to the s polymers of the desir d pr p uch as outer layer of the upper leather and consequent-1 Vinyl acetate, acrylic 8616. y c acid me yl 1y do not cause the grain side of the leather to ethyl esters. meta-acrylic a d e t rs and the become sticky and harden and, after drying, form like mixtures of the a re p ym i y 4 coatings, which adhere satisfactorily to the base, kflfiwn methods, p e y heating n he are fast to water, if desired exert a more or less P n Polymerization accelerators. The water-repelling action and do not impair the p lym need not be carried p natural permeability of the leather. tion. The procedure may rather be adopted of I Particularly suitable compounds are the polycarrying out the process of polymerization only '51 mers of acrylic acid and its esters or the polyto the point of formation of more or less viscous mers of homologues of such compounds, which intermediate products and employing the latter in the solid condition possess the desired propfor the preparation of the aqueous emulsions. erties, such as, tenacity, elasticity, extensibility For the production of the aqueous emulsions 5s and the like. Rubber, for example in the form mixtures of water and organic liquids may also 51 colour.

or longer, if desired at raised temperature, for

example at 40 to C. In many cases it has proved to be advantageous to add alkaline-rm acting substances, particularly ammonia.

In carrying the process of this invention into effect the procedure may for example be followed of working up the leather, which has been subjected to the usual treatments of removing acid, colouring, greasing, burnishing, drying and pressing in order to render the grain compact, into completely fabricated articles, forexample, shoes without the application of further treatments, particularly pounding, and imparting to the same the desired appearance with regard to polish, colour and the like, by applying finishes in accordance with the present invention.

In the manufacture of the leather a layer of mucilage or the like may in this case be applied at any stage of the sequence of operations. On the other hand the repeated application of albumin or blood polishes hitherto customary may be dispensed with. The process of staining or colouring may also be omitted in the manufacture of the leather and the staining or colouring be effected exclusively by the process of finishing according to this invention, alternatively articles may be manufactured from leather, which has been only preliminarly coloured, and the final colour be imparted to these articles on finishing.

The application of the finishes according to this invention is effected in a very simple manner, by applying the same, e. g., by brushing on, for example, to the shoe. By the successive application of several coats special effects may be obtained, for example with regard to polish and The individual coats may contain different polymers of acrylic compounds; they may contain different colouring matters or be in part uncoloured and in part contain colours. When employing colour-containing coats, colour-free finishes may be employed as covering coats. After applying one coat, for example an aqueous emulsion, this is with advantage first allowed to dry for a few minutes, after which the next coat is applied and this again allowed to dry for a few minutes and so on.

The finishes according to this invention adhere fast to the base and, after drying, impart to the article, for example footwear, treated therewith the desired colour and polish, without the leather base being unfavourably influenced, for example by being rendered sticky or hard. The coatings are distinguished by being satisfactorily waterproof and frequently by possessing water-repelling effects. The latter can, if necessary, be further increased by suitable additions.

The invention enables high-grade leather articles, particularly footwear, which fulfil all requirements, particularly with regard to soft texture, fine grain, polish, colour and the like, to be manufactured from non-dressed or only partially dressed, non-coloured or only preliminarily coloured leather. Footwear of any desired colour, shade and polish can be manufactured. Special effects can be produced by applying several colours in succession. It is also possible to colour certain parts of one and the same article of footwear with one colour, and other parts with other colours and in this way to obtain combined effects. The invention also possesses inter alia the great advantage that footwear manufactured from non-colouredv or only partially coloured (preliminarily coloured) leather can be kept in reserve and be subsequently coloured directly before being sold in accordance with the prevailing fashion.

It is already known to prepare solutions or emulsions of compounds of high molecular weight of the kind hereinbefore described and to employ them for the most varied purposes, including the treatment of leather. The use of the hereinbefore described solutions and particularly emulsions as finishes for leather articles, particularly footwear, which have been manufactured from non-dressed or only partially dressed leather is, however, new. It is not possible to produce the effects of the present invention with the known shoe finishes, manufactured from shellac, wax and the like. The hereinbefore described applicability of the solutions and emulsions as finishing agents and the particular advantages accruing from the application of these agents could not have been concluded from the applicability of solutions of polymers of unsaturated compounds and the like substances as agents for the treatment of leather, for example in tanneries. It could in no way have been foreseen that it would be possible, under the application of the finishing agents hereinbefore described, to manufacture leather articles, such as shoes, boots and the like from non-dressed or only partially dressed leather, and to impart to the same the desired polish and colour, without disadvantages appearing.

- Examples 1. 100 parts of a commercial aqueous emulsion of a polymer of acrylic acid derivatives are treatedwlth 5 parts of concentrated aqueous ammonia, allowed to stand for 3 days, at 50 C. and then mixed with 40 to 100 parts of a black pigment, such as is usually used for dressing black leather.

Shoes manufactured from non-dressed leather, which have not been subjected to the usual final dressing treatment, are treated with the aforesaid finish by brushing the latter on and allowing to dry. This treatment is repeated three times and, if desired, a final coat of an emulsion of the acrylic acid derivative polymer, which contains no colouring matter, is applied. The treated shoes have a black colour of excellent appearance. The grain surface of the leather is soft and elastic.

In order to impart a lacquer-like polish to the toe cap, this is two or three times brushed over with an emulsion of a polyvinyl compound, containing no colouring matter, or a colour-free or mars of acrylic acid esters aremixedwith IOOparts 76 of a colouring solution, containing 1 to 2% of a black aniline dye and the same quantity of lampblack pigment, a small quantity of 1% ammonia,

. 0.5% of shellac, 0.3% of Turkey red oil and, if

desired, small quantities of xylene or other organic solvents in addition and preferably subjected, before mixing with the polymer solution, to a boiling down treatment of several hours duration.

The shoes are brushed over two or three times with this finish, each coat being allowed to dry before the application of the next coat.

3. A trunk made of raw leather is brushed over with a coat of a usual brown pigment colour mixture, with the addition of aniline colours and an aqueous emulsion of polymers of acrylic acidand polyvinyl compounds. The edges are then colored in darker tones than the surfaces with a suitably coloured emulsion.

The term "partly dressed leather as used in the specification and claims is intended to cover leather which lies been subjected to the following usual treatments: removing acid, greasing, drying and pressing, and, if desired, coloring, applying a layer of mucilage and burnishing, but which has not been subjected to pounding and to repeated applications of albumin or blood polishes.

What we claim is:

1. A process for the manufacture of finished leather articles which consists in assembling the articles from parts of partly dressed leather and finishing the assembled articles by applying thereto a coating of liquids containing polymers of acrylic compounds which possess the property of drying on with the formation of adhering layers, which are fast to water, tenacious, elastic and extensible and do not harden the grain side of the leather.

2. A process for the manufacture of finished footwear which consists in assembling the footwear from parts of partly dressed leather and finishing the assembled articles by applying thereto a coating of liquids containing polymers of acrylic compounds which possess the property of drying on with the formation of adhering layers, which are fast to water, tenacious, elastic and extensible and do not harden the grain side of the leather.

3. A process according to claim 1, in which said liquids also contain colours, such as pigment colours and organic colours.

4. A process according to claim 1, in which said liquids comprise aqueous emulsions which contain alkaline substances.

5. A process according to claim 1, in which the leather is uncoloured, said liquids also containing colours.

6. A process according to claim 1, in which the leather is preliminarily coloured, said liquids also containing colours.

'7. A process according to claim 1, in which the finishes are applied in several coats, the individual coats containing different polymers of acrylic compounds.

8. A process according to claim 1, in which the finishes are applied in several coats, the individual coats containing different colours.

9. A process according to claim 1, in which the finishes are applied in several coats, some of said coats being colourless and others containing colours.

10. A process according to claim 1, in which the finishes are applied in several coats, said liquids comprising in part aqueous emulsions, and in part solutions.

HANS FREUDENBERG. PHILIP? HAAS. 

